1. Field of the Invention
This invention relates to a rotatable panel cutter for cutting openings in a web and more particularly to a rotatable cutter die having knife side edge portions perpendicular to the longitudinal axis of the rotatable cutter shaft.
2. Description of the Prior Art
Envelopes are conventionally formed from precut envelope blanks having a configuration that includes side flaps, a bottom flap and a closure flap. The envelope blanks are conventionally advanced in succession into a panel cutting mechanism that cuts one or more openings or windows in the body of the envelope blank. Where the envelope blanks are formed from an endless web, it has been the practice in the past to provide panel cutter devices where the cutter shaft and anvil are arranged at an angle of 90.degree. to the center line of the web. Where envelope blanks are formed from an endless web, cutter dies having irregular configurations were required to cut windows or openings in the web before envelope blanks were cut from the web. For example, U.S. Pat. No. 1,111,751 discloses a rotary cutter for cutting eliptical panels in a web before the envelope blanks are severed from the web. The envelope blanks formed in this manner have a generally diamond shape and the eliptical windows are cut at an angle to the side edges of the web. The cutter die disclosed in this patent is limited to the eliptical configuration illustrated therein and the eliptical panels cut in the web are limited to the particular envelope blank configuration disclosed therein.
U.S. Pat. Nos. 3,106,121; 3,257,885; and 3,465,626 disclose panel cutter devices that are employed with severed envelope blanks and are arranged to form one or more rectangular windows therein. These patents discuss positioning the generally rectangular die at an angle to the axis of the panel cutter shaft and also feeding the blanks into the rotary panel cutter at substantially the same angle to provide progressive cutting of the panel in the blank and further to properly orient the panel in parallel relations to the edges of the envelope. In all of these patents, the cutter die has a rectangular configuration to form the rectangular panels in the envelope blank. It was discovered that the generally rectangular cutter dies previously employed in forming panels in envelope blanks did not form rectangular panels in a web of material when the panel cutter dies were positioned to progressively cut the panels in the web. There is a need for a rotary panel cutter and particularly a rotary panel cutter die that is operable to cut windows or openings of a desired configuration in a web as the web is conveyed through the rotatable panel cutter.